Dies and molds are examples of tools that are used in the automotive and other manufacturing industries. Such tools have forming surfaces that are equipped with features for producing a finished product with a desired shape or design. For instance, a die that is used for producing automotive body panels may include a punch and die block assembly having forming surfaces including complementary, opposing surface features. The die parts are mounted in a press, charged with a sheet-metal blank, and then brought together under operating tonnage in order to deform the sheet metal blank therebetween. As the die parts are brought together, the sheet metal blank is stretched and made to conform to the shape of the features that are present on the forming surfaces of the die parts. In this way, automotive body panels having “Tornado Lines” or other design features can be formed.
The fabrication of dies and molds requires significant machining in order to remove unnecessary bulk wrought or cast material, so as to form the forming surfaces having the desired features for making a finished product. Typically, the bulk wrought material is a relatively expensive tool steel alloy or iron. In fact, the cost of producing a finished tool is attributed mainly to the material cost and the amount of machining work that is required. Unfortunately, the process of stretching and deforming sheet metal blanks abrades the forming surfaces of the tool, resulting in considerable “wear and tear” and thereby limiting the useful lifetime of such tools. In particular, sharp features that are used to produce “Tornado Lines” or other similar designs are highly susceptible to wear. This is because the sheet metal blank slides, relative to the sharp features of the tool, to a greater extent than occurs within other portions of the tool, and because the sharp features are more fragile and thus more susceptible to damage and wear compared to other surface portions of the tool. In order to extend the useful lifetime of such tools, it is known to subject sharp features to heat treatment processing in order to increase the material hardness, and thus the wear resistance, of the sharp features. Eventually, however, the tool becomes so worn as to be unusable and it must be repaired, or after a finite number of possible repairs—replaced, at considerable cost. Generally speaking, it is not cost-effective to refurbish such tools.
In WO 2009/077524, a process is described for producing tools from low cost materials, such as high resistance concrete, by casting the low cost material into a desired shape and then coating it with a metallic or ceramic layer. According to this approach, the material cost of the tool is reduced since low cost concrete is used in place of iron alloys, and machining requirements are reduced since only a relatively thin layer of deposited metal or ceramic needs to be removed to define the forming surfaces. Unfortunately, the tools that are produced using this method are somewhat fragile and although they are resistant against high compression loads, their resistance under tensile stress state is low. It is implied that the process is suitable for fabricating low cost tools when the tools do not need to have a very long life cycle.
In WO 2009/090622, a process is described for extending the lifespan of a metal cavity mold. In particular, the process is for repairing defects in molds that are used for making glass articles such as bottles. When a mold becomes worn or damaged a layer of metal is machined off the entire molding surface, then a layer of filler metal that is thicker than the layer of metal removed during the machining step is deposited onto the machined surface, and finally the filler material is machined to the design dimensions for molding the glass articles. Unfortunately, the entire molding surface must be machined in order to repair a defect, which increases cost. Further, it is stated that the filler material for forming the cladding layer must be metallurgically compatible with the cast iron of the mold. This requirement places a restriction on the types of materials that may be used for forming the cladding layer. Consequently, the ability to vary the material properties of the molding surface is limited.
Neither of the above-mentioned processes is suitable for fabricating tools for use in the high volume Class A automotive applications or other similar manufacturing industries. Additionally, neither of the above-mentioned processes achieves reduced material cost of the tool while at the same time allowing for the useful lifetime of the tool to be increased. Further, neither of the above-mentioned processes is suitable for fabricating tools from metallurgically incompatible materials, or from materials that have incompatible mechanical properties.
It would therefore be beneficial to provide a process for fabricating tools, and to provide tools fabricated according to said process, that overcome at least some of the above-mentioned limitations and disadvantages of the prior art.